摘要： CSMA/CD和Token Bus分别是总线网络中采用的竞争策略、无冲突策略的经典信道获取技术。前者在轻载荷下时延较小,却在重载荷下因信道仲裁开销过大使各项性能急剧变差,后者虽在重载荷下有相对确定的时延,但在轻载荷时却时延较大。该文引入一种自适应机制,使网络在轻载荷下运行CSMA/CD协议,而在重载荷下自动转换为Tokcn Bus策略,并通过在应用层配置所编写的协议模块,使传统的非确定性以太网成为自适应实时以太网。

关键词: 虚拟令牌, 自动转换, 实时以太网

Abstract: There are two elassic MAC technologies used in bus-network, CSMA/CD which uses competitive strategy, and Token Bus which uses eollisionless strategy. The time delay of the former is shorter when the load is light, but the performance declines sharply when the load is heavy because of the time-cost for channel arbitration. Although the time delay of the later is definite when the load is heavy, the time delay is longer even the load is light. This paper introduces a self-adaptive method. When the load is light, the network uses CSMA/CD. When the load is heavy, the network turns to use Token Bus automatically. This method can make traditional indefinite Ethernet become self-adaptive real-time network through configuring the protocol module of the application layer.

中图分类号: 

• TP393.11